Spring拦截器搭配注解,实现redis缓存数据

比如用户短时间内多次刷新页面,或app短时间多次请求新内容,可以使用redis缓解请求压力

 

首先自定义注解

/**
 * 标注在controller  进行缓存 ,其他情况不进行
 */
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Cache {

    //默认缓存时间 60秒
    String time() default "60";
}

 

注册config类

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class WebConfig implements WebMvcConfigurer {

    @Autowired
    private RedisCacheInterceptor redisCacheInterceptor;
    @Autowired
    private TokenInterceptor tokenInterceptor;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(this.tokenInterceptor).addPathPatterns("/**");
        registry.addInterceptor(this.redisCacheInterceptor).addPathPatterns("/**");
    }
}

 

注册拦截器

import cn.hutool.crypto.digest.DigestUtil;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import @Cache 包路径;
import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;


/**
 * request的拦截器,全局全内容缓存
 * 关联注解@Cache
 */
@Component
public class RedisCacheInterceptor implements HandlerInterceptor {

    @Value("${tanhua.cache.enable}")
    private Boolean enable;

    @Autowired
    RedisTemplate<String,String> redisTemplate;

    private static final ObjectMapper MAPPER= new ObjectMapper();

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws IOException {
        if (!enable){
            return true;
        }

        if (!(handler instanceof HandlerMethod)){
            return true;
        }

        //判断是不是Get请求
       if (!((HandlerMethod)handler).hasMethodAnnotation(GetMapping.class)){
           return true;
       }

        //controller未加Cache注解
        if (!((HandlerMethod)handler).hasMethodAnnotation(Cache.class)){
            return true;
        }

        //从缓存中取
        String redisKey = createRedisKey(request);
        String data = redisTemplate.opsForValue().get(redisKey);

        //缓存中没有
        if (StringUtils.isEmpty(data)){
            return true;
        }

        //缓存中有
        response.setCharacterEncoding("UTF-8");
        response.setContentType("application/json; charset=utf-8");
        response.getWriter().write(data);
        return false;
    }

    /**
     * 拼接成唯一的redisKey
     * @param request
     * @return
     * @throws JsonProcessingException
     */
    public static String createRedisKey(HttpServletRequest request) throws JsonProcessingException {
        String url = request.getRequestURI();

        String param = MAPPER.writeValueAsString(request.getParameterMap());
        String token = request.getHeader("Authorization");
        String data = url +"_" + param + "_" +token;

        return "SERVER_CACHE_DATA_"+ DigestUtil.md5Hex(data);
    }
}